The present invention relates to methods of fueling an internal combustion engine, specifically a direct injection diesel engine, providing improved nitrogen-free detergency in the engine, particularly in the area of injector deposit control. The present invention also provides methods of providing both improved detergency and improved corrosion inhibition, while avoiding compatibility problems with fuels and/or while limiting the amount of nitrogen delivered to the fuel from the deposit control additive.
Hydrocarbon-based fuels generally contain numerous deposit-forming substances. When used in internal combustion engines (ICE), deposits from these substances can form on and around constricted areas of the engine which come in contact with the fuel. In these ICE, such as automobile engines, deposits can build on engine intake valves and/or fuel injectors leading to progressive restriction of the flow of the fuel mixture into the combustion chamber, in turn reducing the maximum power of the engine, decreasing fuel economy, increasing engine emissions, hindering engine startability, and/or affecting overall drivability.
Engines have and continue to become more sensitive to deposits due at least in part to engine designs utilizing tighter clearances with more constricted areas. A common practice is to incorporate a detergent into the fuel composition for the purpose of reducing or inhibiting the formation of, and facilitating the removal of, engine deposits. These additives improve the engine performance and reduce the engine emissions.
Generally, fuel detergent additives include additives that can be described as ashless dispersants. These additives consist of hydrocarbyl backbones, including polyisobutylene (PIB) backbones, which traditionally have been combined with polar, nitrogen-containing head groups. The primary fuel detergent additives used today include PIB amines, PIB succinimides and PIB phenol Mannich amines. One key aspect of these fuel detergent additives is the presence of an active nitrogen-containing group, which is believed to be required for good performance of the additives.
In some cases, nitrogen-containing additives can lead to undesirable effects, such as seal degradation, particularly in the case of fluoro-elastomer containing seals. Nitrogen-free additives would be free of these potential disadvantages.
There is a need for an effective fuel additive that may be used in fuel additive compositions and fuel compositions in the operation of ICEs that is free of nitrogen. There is need for such nitrogen-free additives that provide comparable and/or improved performance compared to the nitrogen-containing additives commonly used today. There is also a need for these additives to provide improved corrosion inhibition and/or to avoid compatibility issues with the fuels with which they are used. Some of these compatibility issues can lead to unwanted reactions between the fuel and/or one or more additives in the fuel, resulting in byproducts that can hinder engine performance, form deposits and even plug filters. There is a need for additives and fuels compositions, as well as methods of using them, that address one or more of these problems.